1. Field of the Invention
The present invention relates to a liquid discharge head for applying a thermal energy to a liquid to generate a bubble and discharge the liquid, a method of manufacturing the liquid discharge head, and a liquid discharge apparatus using the liquid discharge head.
Moreover, the present invention can be applied to apparatuses for performing recording on recording media such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramic, and the like, such as a printer, a copying machine, a facsimile machine provided with a communication system, and a word processor provided with a printer section, and further to an industrial recording apparatus combined with various processing apparatuses in a composite manner.
Additionally, xe2x80x9crecordingxe2x80x9d in the present invention means not only that a character image, a diagram image or another meaningful image is given to the recording medium, but also that a pattern image or another meaningless image is given.
2. Related Background Art
In conventional recording apparatuses such as a printer, an ink jet recording method, a so-called bubble jet recording method is known which comprises applying heat or another energy to a liquid ink in a flow path to generate a bubble, discharging the ink from a discharge port by an action force based on a steep volume change with the bubble, and attaching the ink to a recording medium to form an image. In a recording apparatus using the bubble jet recording method, as disclosed in U.S. Pat. No. 4,723,129 or the like, the discharge port for discharging the ink, the flow path connected to the discharge port, and an electrothermal converting element as energy generating means, disposed in the flow path, for discharging the ink are usually arranged.
According to the recording method, a high quality level image can be recorded with a high speed and a low noise, and the discharge ports for discharging the ink can be arranged with a high density in a head to perform the recording method, which provides many advantages that a high-resolution recorded image and further a color image can easily be obtained with a small-sized apparatus. Therefore, in recent years the bubble jet recording method has been utilized in many office apparatuses such as a printer, a copying machine, and a facsimile machine, and further in industrial systems such as a textile printing machine.
Various demands have been raised with utilization of such bubble jet technique in products of various fields, and for example, there are proposed drive conditions for providing a liquid discharge method to perform a satisfactory ink discharge with a fast ink discharge speed based on a stable bubble generation in order to obtain a high quality image, or improvement of a flow path configuration to obtain a liquid discharge head fast in refill speed of a discharged liquid into a liquid flow path from a viewpoint of high-speed recording.
Above all, in a head for generating the bubble in a nozzle and discharging the liquid with bubble growth, the bubble growth in a direction opposite to the discharge port and a generated liquid flow are known as factors for deteriorating discharge energy efficiency and refill property, and the invention provided with a structure for enhancing the discharge energy efficiency and refill property is proposed in European Patent Application Laid-Open No. EP0436047A1.
In the invention described in the publication, a first valve, disposed between the vicinity of the discharge port and a bubble generator, for shutting them off, and a second valve, disposed between the bubble generator and an ink supply section, for completely shutting them off are alternately opened/closed (FIGS. 4 to 9 of EP436047A1). For example, in an example of FIG. 7 of the publication, as shown in FIG. 23, a heat generating member 110 is disposed substantially in the middle of an ink flow path 112 between an ink tank 116 and a nozzle 115 on a substrate 125 for forming an inner wall of the ink flow path 112. The heat generating member 110 lies in a division 120 with an entirely closed periphery inside the ink flow path 112. The ink flow path 112 is constituted of the substrate 125, thin films 123, 126 directly laminated on the substrate 125, and ligulate pieces 113, 130 as closing members. The opened ligulate piece is shown by a broken line in FIG. 23. Another thin film 123 extending in a plane parallel to the substrate 125 and terminating in a stopper 124 shuts off on the ink flow path 112. When the bubble is generated in the ink, a free end of the ligulate piece 130 in a nozzle area closely attached to the stopper 126 in a stationary state is displaced upward, and the ink liquid is discharged via the ink flow path 112 and nozzle 115 from the division 120. In this case, since the ligulate piece 113 disposed in an area of the ink tank 116 closely abuts on the stopper 124 in the stationary state, the ink liquid in the division 120 fails to go toward the ink layer 116. When the bubble in the ink vanishes, the ligulate piece 130 is displaced downward to again abut on the stopper 126. Moreover, the ligulate piece 113 falls down in the ink division 120, and accordingly the ink liquid flows into the division 120.
In the invention described in EP0436047A1, however, each of three chambers of the vicinity of the discharge port, bubble generator and ink supply section is divided into two, the ink following a liquid droplet trails long during discharge, and the number of satellite dots considerably increases as compared with an ordinary discharge system for performing bubble growth, shrinkage, and bubble vanishing (it is assumed that an effect of meniscus retreat by the bubble vanishing cannot be used). Moreover, the valve on the side of the bubble discharge port causes much loss of discharge energy. Furthermore, during refill (during ink replenishment to the nozzle) the liquid is supplied to the bubble generator with bubble vanishing, but no liquid can be supplied to the vicinity of the discharge port until the next bubbling occurs, therefore a dispersion of discharged liquid droplet is large, further a discharge response frequency is remarkably small, and a practical level cannot be obtained.
In the present invention, there is proposed an invention for enhancing an inhibition efficiency of a bubble growth component in a direction opposite to a discharge port and contrarily for enhancing a discharge efficiency based on a new idea to find out an inventive method for satisfying a highly efficient refill property and a head constitution.
As a result of intensive researches, the present inventor et al. have found that in a nozzle structure of a liquid discharge head for generating a bubble in a linearly formed nozzle and discharging a liquid with bubble growth, a function of a special check valve inhibits the bubble growth in a (rearward) direction opposite to a discharge port, and a rearward discharge energy can effectively be utilized on a discharge port side. Additionally, it has been found that the special check valve function inhibits a rearward bubble growth component, an efficient refill property is provided, and a discharge response frequency can therefore be set to be considerably high.
Specifically, an object of the present invention is to establish an inventive discharge system (structure) for simultaneously enhancing discharge power and discharge frequency by a nozzle structure and discharge method using an inventive valve function and for achieving a high speed, high image quality head of a level which has not been heretofore achieved.
According to the present invention obtained in the process of the aforementioned research, there is provided a liquid discharge head comprising: a plurality of discharge ports for discharging a liquid; communicates with each of the discharge ports and which comprise a bubble generating area for generating a bubble in the liquid; bubble generating means for generating an energy to generate and grow the bubble; a plurality of liquid supply ports, disposed in the plurality of liquid flow paths, respectively, for communicating with a common liquid supply chamber; and a movable member having a free end supported at a slight gap with respect to the side of the liquid flow path of the liquid supply port. An area surrounded with at least a free end portion of the movable member and both side portions continued from the free end portion is larger than an opening area to the liquid flow path of the liquid supply port. A period when the movable member seals and substantially shuts off the opening area is provided from when a drive voltage is applied to the bubble generating means until a period of substantial isotropic growth of the entire bubble by the bubble generating means ends. After the period when the movable member seals and substantially shuts off the opening area, and while a portion of the bubble generated by the bubble generating means on the side of the discharge port grows, the movable member starts displacement on the side of the bubble generating means inside the liquid flow path, and liquid supply is enabled to the liquid flow path from the common liquid supply chamber. When a volume of a liquid droplet discharged from the discharge port is Vd, and during discharge of the liquid from the discharge port, a drawing volume from the discharge port to a liquid surface retracted to maximum into the liquid flow path is Vm, a relation of Vd greater than Vm is established.
The slight gap between the movable member and the liquid supply port is preferably about 10 xcexcm or less.
A discharge direction of the liquid from the discharge port substantially crosses at right angles to a normal direction of a surface on which the bubble generating means is disposed, or the discharge port is supposedly disposed opposite to the bubble generating means.
Moreover, according to the present invention, there is provided a liquid discharge apparatus comprising: the aforementioned liquid discharge head; and recording medium conveying means for conveying a recording medium to receive the liquid discharged from the liquid discharge head. In this case, it is considered that an ink is discharged from the liquid discharge head, and attached to the recording medium to perform recording.
Further, according to the present invention, there is provided a liquid discharging method utilizing a liquid discharge head comprising:
a plurality of discharge ports for discharging a liquid;
a plurality of liquid flow paths whose one end portion always communicates with each of said discharge ports and which comprise a bubble generating area for generating a bubble in the liquid;
bubble generating means for generating an energy to generate and grow said bubble;
a plurality of liquid supply ports, disposed in said plurality of liquid flow paths, respectively, for communicating with a common liquid supply chamber; and
a movable member having a free end supported at a slight gap with respect to the side of said liquid flow path of said liquid supply port,
wherein an area surrounded with at least a free end portion of said movable member and both side portions continued from the free end portion is larger than an opening area to the liquid flow path of said liquid supply port,
a period when said movable member seals and shuts off said opening area is provided from when a drive voltage is applied to said bubble generating means until a period of isotropic growth of the entire bubble by said bubble generating means ends,
after the period when said movable member seals and shuts off said opening area, and while a portion of the bubble generated by said bubble generating means on the side of said discharge port grows, said movable member starts displacement on the side of said bubble generating means inside said liquid flow path, and liquid supply is enabled to said liquid flow path from said common liquid supply chamber, and
when a volume of a liquid droplet discharged from said discharge port is Vd, and
during the discharge of the liquid from said discharge port, a drawing volume from the discharge port to a liquid surface retracted to maximum into said liquid flow path is Vm,
a relation of Vd greater than Vm is established.
In the aforementioned constitution, from when the drive voltage is applied to the bubble generating means, until the period of the substantial isotropic growth of the entire bubble by the bubble generating means ends, a communication state between the liquid flow path and the liquid supply port is immediately shut off by the movable member. Therefore, a pressure wave by the bubble growth in the bubble generating area fails to be propagated to the side of the liquid supply port and common liquid supply chamber, a most part of the wave is directed to the discharge port side, and the discharge power is rapidly enhanced. Moreover, even when a recording liquid with a high viscosity is used to fix the liquid to a recording sheet or the like at a high speed or to eliminate blur in a boundary of black and another color, the liquid can satisfactorily be discharged by the rapid enhancement of the discharge power. Moreover, with an environmental change during recording, particularly under an environment with low temperature and low humidity an ink thickening area increases in the discharge port, and the ink fails to be ordinarily discharged at the start of use in some cases, but in the present invention the ink can satisfactorily be discharged from first. Moreover, since the discharge power is rapidly enhanced, for example, by reducing a size of a heat generating member for use as bubble generating means, an energy to be projected for the discharge can be reduced.
Moreover, the movable member is displaced to the side of the bubble generating means with bubble shrinkage, the liquid rapidly flows into the liquid flow path via the liquid supply port from the common liquid supply chamber, and a flow for drawing a meniscus after the discharge into the liquid flow path from the discharge port rapidly decreases. Thereby, a retreat amount of meniscus in the discharge port after liquid droplet discharge decreases. As a result, after the discharge, the meniscus returns to its initial state in a very short time. Specifically, since a time for completing refilling of a constant amount of ink to the liquid flow path is short, even the discharge frequency (drive frequency) can rapidly be enhanced in performing a high-precision (constant-amount) ink discharge.
Other effects of the present invention will be understood from description of respective embodiments.
Additionally, xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d for use in the description of the present invention are represented with respect to a flow direction of the liquid toward the discharge port from a liquid supply source via the bubble generating area (or the movable member), or with respect to a constitutional direction.
Moreover, xe2x80x9cdownstream sidexe2x80x9d regarding the bubble itself means the bubble generated on a downstream side of the flow direction or the constitutional direction with respect to a bubble center, or in an area on the downstream side from an area center of the heat generating member.
Furthermore, expression xe2x80x9cthe movable member seals and substantially shuts off the liquid supply portxe2x80x9d in the present invention includes a case in which the movable member does not necessarily closely abut on the peripheral portion of the liquid supply port, and limitless approaches the liquid supply port.